Incandescent electric lamp.



No. 654,208. Patented July 24, I900.

S. D. WASHBURN &. C. H. TINKHAM.

INCANDESCENT ELECTRIC LAMP:

(Application filed Jan. 23, 1899.)

(No Model.)

MWWZ .2 iggw f zyflwz'r aizorneys,

Ilwrrnn 'rnrns SAMUEL DEXTER'WASHBURN, OF BOSTON, AND CLARENCE HERBERTTINKHAM, OF CAMBRIDGE, MASSACHUSETTS.

INCANDESQENT ELECTRIC LAM P.

SPECIFICATION forming part of Letters Patent No. 654,208, dated July 24,1900. Application filed January 23, 1899. Serial No. 703.064. (Nomodel.)

To all whom it may concern:

Be it known that we, SAMUEL DEXTER WASHBURN, of Boston, in the county ofSuffolk, and CLARENCE HERBERT TINKHAM, of Cambridge, in the county ofMiddlesex, in the Stateof Massachusetts, have invented an ImprovedIncandesccnt Electric Lamp, of which the following is a specification,reference being had to the accompanying drawings, in which- Figure 1 isan elevation of one of our lamps. Fig. 2 is a section on line 2 2 ofFig. 1. Fig. 3 is a section on line 3 3 of Fig. 1. Fig. 4 is anelevation, partly in section, of another form of our lamp.

In our pending application, Serial No. 684,456, filed June 525, 1898, wehave described a lamp consisting of a glass bulb sealed to a glassvessel, the base of which is a mirror, and a zigzag filament across theconcave face of that mirror; and our present invention is an improvementon that lamp which while retaining both of those features in substanceis a practical improvement, as it facilitates the manufacture, therebydecreasing the cost and also increases the life of the lamp and in somedegree increases the candle-power, as our new mirrors are practicallymore efficient than that described in our pending application.

In the drawings, A is a tube of glass closed at its inner end, and Aa'mirror connected by the wire 0. to the inner closed end of tube A.This mirror A, as described in Figs. 1, 2, and 3, is formed of a thindisk C6 of metal, capable of a high polish, spun over a thin disk a ofglass, concave on one side and convex on the other side, like theordinary watchcrystal. One end of the wire a is soldered to the metaldisk a and the other end covered with glass, which is fused to the innerend of tube A.

The leading-in wires pass through tube A and are sealed in the closedend of that tube and united to the filament B in the usual way. Smallinsulating-tubes b b are formed about the leading in wires to preventelectrical contact with the metal disk at, and these insulating-tubes bh occupy holes through the metal disk at and the glass disk a Inassembling the parts bulb D is first made and the capillary (I attachedin the usual way,

except that the neck of bulb D is left of sufficient diameter to enabletube A, with the leading-in wires and mirror A attached, to be droppedinto bulb D. Then the neck of bulb D is drawn down to the desired shapeand its mouth sealed to the mouth of tube A after tube A has beenproperly placed to bring mirror A into the desired position. Thecapillary cl may of course be attached to the neck end of bulb D, as isnow often practiced. The bulb D is then exhausted and the lamp finishedas usual.

In some of our lamps embodying the present invention the bulb D wasbroken into two parts along the line 3 3, and the tube A, with theleading-in Wires and mirror A attached, was dropped in and the two partsof bulb D then sealed together; but while this is a convenient andexcellent way of assembling the parts it requires the bulb D to be madeof a greater diameter toward the neck end, as indicated by the dottedline of Fig. 2, and this requires the wire to be heavier in order togive a proper support to the mirror.

In the lamp described in our pending application, Serial No. 684,456, wedescribe the filament as zigzag, and while this is an important matterwe have discovered that a helical filament has all the advantages of ourzigzag filament and, as will be clear from Fig. 3, is in point of factzigzag, and this discovery is one feature of our present invention.

For certain uses a mirror made of porcelain glazed in its concavesurface is better than the metal and watch crystal mirror abovedescribed, and this form of our invention is shown in Fig. 4, but needsno description, except that the supporting-wire a is headed and passedthrough a hole in the mirror A instead of being connected by solder asbefore; but this is of course a mere detail of construction.

What we claim as our invention is- 1. In an incandescentelectriclampincombination, a bulb; a tube of glass closed at its inner end and sealedto the bulb; leading-in wires sealed in the tube; a mirror; and a wireone end of which is fast to the tube and the other end to the mirror,substantially as described.

2. In an incandescent electric lampin combination a bulb; a tube closedat one end and sealed to the bulb; a mirror crosswise of the bulb; awire one end of which is fastto the tube and the other end to themirror; a filament in the form of a helix the axis of the helicalfilament being substantially parallel with the surface of the mirror;and leadingin wires sealed in the tube and passing through the mirrorand insulated therefrom to the ter 10 minals of the helical filament.

3. In combination, the bulb; the tube of glass closed at its inner endand sealed to the bulb; the mirror; the wire fast at one end to themirror and at the other end to the tube; the helical filament; and theleading-in wires sealed in the tube and connected to the terminals ofthe helical filament.

SAMUEL DEXTER WASHBURN. CLARENCE HERBERT TINKIIAM:

H. POWERS,

Witnesses i H. P. GUILLo.

